496 



CENOZOIC TIME. 



phosphatic deposits, partly nodular in structure, and often containing Eocene fossils. 

 Their origin is explained, by Prof. C. U. Shepard, by supposing that the Eocene beds 

 were covered by extensive guano deposits, and that the percolating waters, carrying 

 down carbonic acid and soluble phosphates, decomposed and carried off part of the 

 Eocene, and altered other portions to phosphates, just as has happened on the Guano 

 islands of the Caribbean sea, where underlying corals and shells are converted into 

 phosphate of lime by a similar process. 



II. Life. 

 1. Plants. 

 1. Protophytes. — About one hundred species of Diatoms have been 

 described by Ehrenberg and Bailey, from the Infusorial stratum of 



Fig. 882. 



•<^^ 



gar 



Richmond Infusorial Earth. — a, Pinnularia peregrina ; b, c, Odontidium pimmlatum; d, ) 

 Grammatophora marina ; e, SpoDgiolithis appendiculata ; /, Melosira sulcata ; g, transverse view, 

 id. ; A, Actinocyclus Ehrenbergii ; ?', Coscinodiscus apiculatus ; j, Triceratium obtusum ; k, Actin- 

 optychusundulatus; I, Dictyocha crux ; m, Dictyocha ; n, fragment of a segment of Actinop- 

 tychus senarius ; o, Navicula; p, fragment of Coscinodiscus gigas. 



Richmond, besides a few Polycystines (siliceous Foraminifers) and 

 many sponge-spicules. Fig. 882 represents a portion of the Richmond 

 earth, as it appeared in the field of view of Ehrenberg's microscope. 

 This is an example of one of the many Infusorial earths of the era. 

 2. Angiosperms, Conifers, Palms. — The Lignitic and coal-bearing 



